Dual component LLDPE copolymers with improved impact and tear resistance

ABSTRACT

Disclosed are ethylene polymer compositions containing a homogeneously-branched first ethylene polymer component and a homogeneously-branched second ethylene polymer component of higher density than the first ethylene polymer component. The ethylene polymer composition can be characterized by a density from 0.912 to 0.925 g/cm 3 , a melt index less than 3.5 g/10 min, and a CY-a parameter at 190° C. from 0.25 to 0.65. These polymer compositions have the excellent dart impact strength and optical properties of a metallocene-catalyzed LLDPE, but with improved machine direction tear resistance, and can be used in blown film and other end-use applications.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/459,656, filed on Jul. 2, 2019, now U.S. Pat.No. 10,544,273, which is a continuation application of U.S. patentapplication Ser. No. 15/715,215, filed on Sep. 26, 2017, now U.S. Pat.No. 10,435,527, the disclosures of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

Polyolefins such as high density polyethylene (HDPE) homopolymer andlinear low density polyethylene (LLDPE) copolymer can be produced usingvarious combinations of catalyst systems and polymerization processes.Ziegler-Natta and chromium-based catalyst systems can, for example,produce ethylene polymers having good extrusion processability andpolymer melt strength and bubble stability in blown film applications,typically due to their broad molecular weight distribution (MWD).Further, films produced using Ziegler-Natta catalyst systems have goodtear resistance in both the machine direction (MD) and the transversedirection (TD), but generally suffer from poor impact strength. Incontrast, metallocene-based catalyst systems can, for example, produceethylene polymers having excellent impact strength and opticalproperties, but often lack superior tear resistance, particularly in themachine direction.

In some end-uses, such as blown film applications, it can be beneficialto have the impact resistance and optical properties of ametallocene-catalyzed LLDPE copolymer, but with improved MD tearresistance. Accordingly, it is to these ends that the present inventionis generally directed.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify required oressential features of the claimed subject matter. Nor is this summaryintended to be used to limit the scope of the claimed subject matter.

The present invention generally relates to ethylene polymer compositionscontaining (i) a homogeneously-branched first ethylene polymercomponent, and (ii) a homogeneously-branched second ethylene polymercomponent of higher density than the first ethylene polymer component.Generally, the amount of the second ethylene polymer component can be ina range from about 4 to about 50 wt. %, from about 4 to about 25 wt. %,or from about 10 to about 25 wt. %, based on the total weight of thefirst ethylene polymer component and the second ethylene polymercomponent. The ethylene polymer composition can be characterized by adensity in a range from about 0.912 to about 0.925 g/cm³, a melt indexless than or equal to about 3.5 g/10 min, and a CY-a parameter at 190°C. in a range from about 0.25 to about 0.65. The first ethylene polymercomponent often can have a density in a range from about 0.89 to about0.922 g/cm³ (or from about 0.905 to about 0.918 g/cm³), while the secondethylene polymer component can have a density in a range from about 0.93to about 0.972 g/cm³ (or from about 0.945 to about 0.968 g/cm³).

Additionally or alternatively, the ethylene polymer composition can havean ATREF profile characterized by at least two peaks, with a first peak(a lower temperature peak) at a temperature in a range from about 67 toabout 82° C. (or from about 68 to about 80° C.), and a second peak (ahigher temperature peak) at a temperature in a range from about 92 toabout 105° C. (or from about 96 to about 105° C.). Moreover, thedifference between the temperatures of the two peaks (ΔT) often can fallwithin a range from about 17 to about 32° C. (or from about 18 to about30° C.).

These ethylene polymer compositions, in further aspects, can becharacterized by a melt index (MI) in a range from about 0.3 to about 2g/10 min (or from about 0.5 to about 1.8 g/10 min), and/or a ratio ofHLMI/MI in a range from about 10 to about 35 (or from about 12 to about22), and/or a ratio of Mw/Mn in a range from about 1.8 to about 4.5 (orfrom about 2.2 to about 3.8), and/or a ratio of Mz/Mw in a range fromabout 1.6 to about 2.5 (or from about 1.7 to about 2.1), and/or a Mw ina range from about 85 to about 200 kg/mol (or from about 100 to about180 kg/mol), and/or a zero-shear viscosity in a range from about 2,500to about 25,000 Pa-sec (or from about 3,000 to about 20,000 Pa-sec),and/or less than 10 long chain branches (or less than 5 long chainbranches) per million total carbon atoms, and/or a number of short chainbranches per 1000 total carbon atoms of the polymer composition at Mwthat is greater than at Mn (or at Mz that is greater than at Mn).Moreover, in some aspects of this invention, the polymer composition cancontain no measurable amount of hafnium or titanium, i.e., less than 0.1ppm, and often less than 0.05 ppm.

These ethylene polymer compositions can be used to produce variousarticles of manufacture, such as films (e.g., blown films), sheets,pipes, geomembranes, and molded products.

Both the foregoing summary and the following detailed descriptionprovide examples and are explanatory only. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Further, features or variations may be provided inaddition to those set forth herein. For example, certain aspects andembodiments may be directed to various feature combinations andsub-combinations described in the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 presents a plot of the second heat DSC curves for low densitycomponent LD 1, high density component HD 1, and ethylene polymercomposition B16.

FIG. 2 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B1-B6.

FIG. 3 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B16-B19.

FIG. 4 presents a plot of the logarithm of the zero-shear viscosityversus the logarithm of weight-average molecular weight (Mw) for theethylene polymer compositions of Examples B1-B15.

DEFINITIONS

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2nd Ed (1997), can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Herein, features of the subject matter are described such that, withinparticular aspects, a combination of different features can beenvisioned. For each and every aspect and/or feature disclosed herein,all combinations that do not detrimentally affect the designs,compositions, processes, and/or methods described herein arecontemplated with or without explicit description of the particularcombination. Additionally, unless explicitly recited otherwise, anyaspect and/or feature disclosed herein can be combined to describeinventive features consistent with the present disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsor steps, unless stated otherwise. For example, an ethylene polymercomposition consistent with aspects of the present invention cancomprise; alternatively, can consist essentially of; or alternatively,can consist of; a first ethylene polymer component and a second ethylenepolymer component.

The terms “a,” “an,” “the,” etc., are intended to include pluralalternatives, e.g., at least one, unless otherwise specified.

Generally, groups of elements are indicated using the numbering schemeindicated in the version of the periodic table of elements published inChemical and Engineering News, 63(5), 27, 1985. In some instances, agroup of elements can be indicated using a common name assigned to thegroup; for example, alkali metals for Group 1 elements, alkaline earthmetals for Group 2 elements, transition metals for Group 3-12 elements,and halogens or halides for Group 17 elements.

The term “polymer” is used herein generically to include ethylenehomopolymers, copolymers, terpolymers, and the like, as well as alloysand blends thereof. The term “polymer” also includes impact, block,graft, random, and alternating copolymers. A copolymer is derived froman olefin monomer and one olefin comonomer, while a terpolymer isderived from an olefin monomer and two olefin comonomers. Accordingly,“polymer” encompasses copolymers and terpolymers derived from ethyleneand any comonomer(s) disclosed herein. Similarly, the scope of the term“polymerization” includes homopolymerization, copolymerization, andterpolymerization. Therefore, an ethylene polymer would include ethylenehomopolymers, ethylene copolymers (e.g., ethylene/α-olefin copolymers),ethylene terpolymers, and the like, as well as blends or mixturesthereof. Thus, an ethylene polymer encompasses polymers often referredto in the art as LLDPE (linear low density polyethylene) and HDPE (highdensity polyethylene). As an example, an ethylene copolymer can bederived from ethylene and a comonomer, such as 1-butene, 1-hexene, or1-octene. If the monomer and comonomer were ethylene and 1-hexene,respectively, the resulting polymer could be categorized an asethylene/1-hexene copolymer. The term “polymer” also includes allpossible geometrical configurations, unless stated otherwise, and suchconfigurations can include isotactic, syndiotactic, and randomsymmetries. Moreover, unless stated otherwise, the term “polymer” alsois meant to include all molecular weight polymers.

The terms “catalyst composition,” “catalyst mixture,” “catalyst system,”and the like, do not depend upon the actual product or compositionresulting from the contact or reaction of the initial components of thedisclosed or claimed catalyst composition/mixture/system, the nature ofthe active catalytic site, or the fate of the co-catalyst, themetallocene compound, or the activator (e.g., activator-support), aftercombining these components. Therefore, the terms “catalyst composition,”“catalyst mixture,” “catalyst system,” and the like, encompass theinitial starting components of the composition, as well as whateverproduct(s) may result from contacting these initial starting components,and this is inclusive of both heterogeneous and homogenous catalystsystems or compositions. The terms “catalyst composition,” “catalystmixture,” “catalyst system,” and the like, can be used interchangeablythroughout this disclosure.

Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of theinvention, the typical methods, devices, and materials are hereindescribed.

All publications and patents mentioned herein are incorporated herein byreference for the purpose of describing and disclosing, for example, theconstructs and methodologies that are described in the publications,which might be used in connection with the presently describedinvention.

Several types of ranges are disclosed in the present invention. When arange of any type is disclosed or claimed, the intent is to disclose orclaim individually each possible number that such a range couldreasonably encompass, including end points of the range as well as anysub-ranges and combinations of sub-ranges encompassed therein. Forexample, by a disclosure that the ratio of Mz/Mw can be in a range fromabout 1.6 to about 2.5, the intent is to recite that the ratio of Mz/Mwcan be any ratio in the range and, for example, can be equal to about1.6, about 1.7, about 1.8, about 1.9, about 2, about 2.1, about 2.2,about 2.3, about 2.4, or about 2.5. Additionally, the ratio of Mz/Mw canbe within any range from about 1.6 to about 2.5 (for example, from about1.8 to about 2.3), and this also includes any combination of rangesbetween about 1.6 and about 2.5. Likewise, all other ranges disclosedherein should be interpreted in a manner similar to this example.

The term “about” means that amounts, sizes, formulations, parameters,and other quantities and characteristics are not and need not be exact,but may be approximate and/or larger or smaller, as desired, reflectingtolerances, conversion factors, rounding off, measurement errors, andthe like, and other factors known to those of skill in the art. Ingeneral, an amount, size, formulation, parameter or other quantity orcharacteristic is “about” or “approximate” whether or not expresslystated to be such. The term “about” also encompasses amounts that differdue to different equilibrium conditions for a composition resulting froma particular initial mixture. Whether or not modified by the term“about,” the claims include equivalents to the quantities. The term“about” can mean within 10% of the reported numerical value, preferablywithin 5% of the reported numerical value.

As used herein, “MD” refers to machine direction, and “CD” refers tocross direction. The cross direction also can be referred to herein asthe transverse direction (TD).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed generally to ethylene polymercompositions containing a lower density component and a higher densitycomponent. Articles produced from these ethylene-based polymercompositions, such as blown films, can have excellent dart impact, tearstrength (e.g., MD Elmendorf tear strength), and optical properties,despite the presence of the higher density component in the polymercomposition.

Ethylene Polymer Compositions

Generally, the ethylene polymer compositions disclosed herein contain(i) a homogeneously-branched first ethylene polymer component, and (ii)a homogeneously-branched second ethylene polymer component of higherdensity than the first ethylene polymer component. The first ethylenepolymer component and the second ethylene polymer component areethylene-based polymers, or ethylene polymers, encompassing homopolymersof ethylene as well as copolymers, terpolymers, etc., of ethylene and atleast one olefin comonomer. Comonomers that can be copolymerized withethylene often can have from 3 to 20 carbon atoms in their molecularchain. For example, typical comonomers can include, but are not limitedto, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, andthe like, or combinations thereof. In an aspect, the olefin comonomercan comprise a C₃-C₁₈ olefin; alternatively, the olefin comonomer cancomprise a C₃-C₁₀ olefin; alternatively, the olefin comonomer cancomprise a C₄-C₁₀ olefin; alternatively, the olefin comonomer cancomprise a C₃-C₁₀ α-olefin; alternatively, the olefin comonomer cancomprise a C₄-C₁₀ α-olefin; alternatively, the olefin comonomer cancomprise 1-butene, 1-hexene, 1-octene, or any combination thereof; oralternatively, the comonomer can comprise 1-hexene. Typically, theamount of the comonomer, based on the total weight of monomer (ethylene)and comonomer, can be in a range from about 0.01 to about 20 wt. %, fromabout 0.1 to about 10 wt. %, from about 0.5 to about 15 wt. %, fromabout 0.5 to about 8 wt. %, or from about 1 to about 15 wt. %.

In one aspect, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component of thisinvention, independently, can comprise an ethylene/α-olefin copolymerand/or an ethylene homopolymer. Thus, the ethylene polymer composition,in some aspects, can comprise an ethylene/α-olefin copolymer and anethylene homopolymer.

In another aspect, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component,independently, can comprise an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, an ethylene/1-octene copolymer, an ethylenehomopolymer, or any combination thereof; alternatively, anethylene/1-butene copolymer, an ethylene/1-hexene copolymer, anethylene/1-octene copolymer, or any combination thereof; oralternatively, an ethylene/1-hexene copolymer. Consistent with aspectsof the present invention, the ethylene polymer composition, the firstethylene polymer component, and the second ethylene polymer component,independently, can have any of the polymer properties listed below andin any combination, unless indicated otherwise.

The ethylene polymer composition can be characterized by a density in arange from about 0.912 to about 0.925 g/cm³. For example, the ethylenepolymer composition can have a density in a range from about 0.912 toabout 0.922 g/cm³; alternatively, from about 0.912 to about 0.92 g/cm³;or alternatively, from about 0.915 to about 0.925 g/cm³.

The first ethylene polymer component is a lower density component, i.e.,the first ethylene polymer component has a lower density than that ofthe second ethylene polymer component. In one aspect, the first ethylenepolymer component can have a density in a range from about 0.89 to about0.922 g/cm³, while in another aspect, the density can be in a range fromabout 0.90 to about 0.92 g/cm³, and in yet another aspect, from about0.905 to about 0.918 g/cm³, and in still another aspect, from about 0.91to about 0.918 g/cm³. The second ethylene polymer component is a higherdensity component, i.e., the second ethylene polymer component has ahigher density than that of the first ethylene polymer component. In oneaspect, for instance, the second ethylene polymer component can have adensity in a range from about 0.93 to about 0.972 g/cm³, while inanother aspect, the density can be in a range from about 0.932 to about0.97 g/cm³, and in yet another aspect, from about 0.93 to about 0.958g/cm³, and in still another aspect, from about 0.945 to about 0.968g/cm³.

While not being limited thereto, the amount of the second ethylenepolymer component often can be in a range from about 4 to about 50 wt.%, from about 4 to about 40 wt. %, from about 4 to about 25 wt. %, orfrom about 4 to about 15 wt. %, based on the total weight of the firstethylene polymer component and the second ethylene polymer component. Inother aspects, the amount of the second ethylene polymer component canbe in a range from about 10 to about 40 wt. %, from about 10 to about 25wt. %, from about 10 to about 20 wt. %, or from about 20 to about 30 wt.%, etc., based on the total weight of the first ethylene polymercomponent and the second ethylene polymer component.

The respective melt index (MI) of the ethylene polymer composition andthe first ethylene polymer component, independently, can be less than orequal to about 3.5 g/10 min, less than or equal to about 2.5 g/10 min,or less than or equal to about 1.5 g/10 min. Typical ranges for the MIof the ethylene polymer composition and/or the first ethylene polymercomponent can include, but are not limited to, from about 0.3 to about 3g/10 min, from about 0.3 to about 2 g/10 min, from about 0.5 to about2.5 g/10 min, from about 0.5 to about 1.8 g/10 min, or from about 0.7 toabout 1.7 g/10 min.

The melt index of the second ethylene polymer component generally is notnecessarily limited to the same ranges as that of the first ethylenepolymer component. For instance, the second ethylene polymer componentcan have a MI of less than or equal to about 50 g/10 min, less than orequal to about 40 g/10 min, or less than or equal to about 10 g/10 min,with representative non-limiting ranges including from about 0.3 toabout 2 g/10 min, from about 0.5 to about 40 g/10 min, from about 5 toabout 40 g/10 min, from about 0.4 to about 12 g/10 min, and from about10 to about 50 g/10 min.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of HLMI/MI (high load melt index/melt index) in a range from about10 to about 35, from about 15 to about 35, from about 15 to about 28,from about 15 to about 25, from about 12 to about 30, or from about 12to about 22, and the like.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of Mw/Mn, or polydispersity index, in a range from about fromabout 1.8 to about 4.5, from about 1.8 to about 4, or from about 2 toabout 4, in some aspects of this invention, and from about 2.2 to about4, from about 2 to about 3.8, or from about 2.2 to about 3.8, in otheraspects of this invention.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of Mz/Mw in a range from about 1.6 to about 2.5, or from about 1.7to about 2.3, in some aspects of this invention, and from about 1.8 toabout 2.3, from about 1.8 to about 2.2, or from about 1.7 to about 2.1,in other aspects of this invention.

The respective weight-average molecular weight (Mw) of the ethylenepolymer composition and the first ethylene polymer component,independently, can be from about 85 to about 200 kg/mol, or from about85 to about 150 kg/mol. Other suitable ranges include from about 100 toabout 200 kg/mol, from about 100 to about 180 kg/mol, or from about 100to about 150 kg/mol.

The Mw of the second ethylene polymer component generally is notnecessarily limited to the same ranges as that of the first ethylenepolymer component. For instance, the second ethylene polymer componentcan have a Mw from about 85 to about 200 kg/mol, from about 85 to about160 kg/mol, or from about 100 to about 200 kg/mol, in some aspects ofthis invention, and from about 40 to about 180 kg/mol, or from about 40to about 150 kg/mol, in other aspects of this invention.

Consistent with one aspect of this invention, the Mw of the firstethylene polymer component can be greater than the Mw of the secondethylene polymer component. In this aspect, the ratio of the Mw of thefirst ethylene polymer component to the Mw of the second ethylenepolymer component typically can fall within a range from about 1.1:1 toabout 2.5:1, from about 1.1:1 to about 2:1, from about 1.1:1 to about1.8:1, or from about 1.2:1 to about 2.5:1.

Consistent with another aspect of this invention, the Mw of the firstethylene polymer component can be less than the Mw of the secondethylene polymer component. In this aspect, the ratio of the Mw of thefirst ethylene polymer component to the Mw of the second ethylenepolymer component typically can fall within a range from about 0.5:1 toabout 0.9:1, from about 0.6:1 to about 0.9:1, from about 0.65:1 to about0.9:1, or from about 0.7:1 to about 0.9:1.

Consistent with yet another aspect of this invention, the Mw of thefirst ethylene polymer component can be substantially the same as thatof the Mw of the second ethylene polymer component (of similar molecularsize). In this aspect, the ratio of the Mw of the first ethylene polymercomponent to the Mw of the second ethylene polymer component typicallycan fall within a range from about 0.75:1 to about 1.25:1, from about0.8:1 to about 1.2:1, from about 0.9:1 to about 1.1:1, or from about0.8:1 to about 1.1:1.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aunimodal molecular weight distribution (as determined using gelpermeation chromatography (GPC) or other suitable analytical technique).In a unimodal molecular weight distribution, there is a singleidentifiable peak. Often, each of the ethylene polymer composition, thefirst ethylene polymer component, and the second ethylene polymercomponent, has a unimodal molecular weight distribution.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aCY-a parameter (at 190° C.) in a range from about 0.25 to about 0.65;alternatively, from about 0.25 to about 0.6; alternatively, from about0.3 to about 0.65; alternatively, from about 0.35 to about 0.65;alternatively, from about 0.4 to about 0.65; or alternatively, fromabout 0.45 to about 0.65.

The respective zero-shear viscosity (at 190° C.) of the ethylene polymercomposition and the first ethylene polymer component, independently, canbe from about 2,500 to about 25,000 Pa-sec, or from about 3,000 to about25,000 Pa-sec. Other suitable ranges include from about 2,500 to about20,000 Pa-sec, from about 3,000 to about 20,000 Pa-sec, or from about4,000 to about 15,000 Pa-sec.

The zero-shear viscosity (at 190° C.) of the second ethylene polymercomponent generally is not necessarily limited to the same ranges asthat of the first ethylene polymer component. For instance, the secondethylene polymer component can have a zero-shear viscosity from about2,500 to about 25,000 Pa-sec, or from about 5,000 to about 70,000Pa-sec, in some aspects of this invention, and from about 150 to about2,500 Pa-sec, or from about 500 to about 5,000 Pa-sec, in other aspectsof this invention.

The zero-shear viscosity and the CY-a parameter are determined fromviscosity data measured at 190° C. and using the Carreau-Yasuda (CY)empirical model as described herein.

The ethylene polymer composition, the first ethylene polymer component,and the second ethylene polymer component typically have low levels oflong chain branches (LCB). For instance, the ethylene polymercomposition, the first ethylene polymer component, and the secondethylene polymer component independently, can have less than 10 longchain branches (LCB), less than 8 LCB, less than 5 LCB, or less than 3LCB, per million total carbon atoms.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component, can have areverse short chain branching distribution (reverse SCBD; increasingcomonomer distribution) or a flat short chain branching distribution(flat SCBD; uniform comonomer distribution). As one of skill in the artwould readily recognize, the profile of the SCBD is not applicable whenthe second ethylene polymer component is an ethylene homopolymer.

A reverse SCBD can be characterized by the number of short chainbranches (SCB) per 1000 total carbon atoms of the ethylene polymer at Mwthat is greater than at Mn, and/or the number of SCB per 1000 totalcarbon atoms of the ethylene polymer at Mz that is greater than at Mw,and/or the number of SCB per 1000 total carbon atoms of the ethylenepolymer at Mz that is greater than at Mn.

A flat SCBD can be characterized by a slope of a plot of the number ofshort chain branches (SCB) per 1000 total carbon atoms versus thelogarithm of molecular weight of the ethylene polymer (determined vialinear regression over the range from D15 to D85) that is in a rangefrom about −0.6 to about 0.6, and/or a percentage of data pointsdeviating from the average short chain branch content by greater than0.5 short chain branches per 1000 total carbon atoms (determined overthe range from D15 to D85) that is less than or equal to about 20%,and/or a percentage of data points deviating from the average shortchain branch content by greater than 1 short chain branch per 1000 totalcarbon atoms (determined over the range from D15 to D85) that is lessthan or equal to about 10%. Polymers having a flat or uniform SCBD aredisclosed, for example, in U.S. Pat. Nos. 9,217,049 and 9,574,031, whichare incorporated herein by reference in their entirety.

In accordance with certain aspects of this invention, the ethylenepolymer compositions described herein can have a unique ATREF profile.For instance, the ethylene polymer composition can be characterized byan ATREF curve containing at least two peaks (in the 60-110° C. range),with a first peak (a lower temperature peak) at a temperature in a rangefrom about 67 to about 82° C., from about 70 to about 82° C., from about68 to about 80° C., or from about 70 to about 80° C. Additionally oralternatively, the ethylene polymer composition can be characterized byan ATREF curve containing at least two peaks (in the 60-110° C. range),with a second peak (a higher temperature peak) at a temperature in arange from about 92 to about 105° C., from about 94 to about 105° C.,from about 95 to about 105° C., or from about 96 to about 105° C.

Additionally or alternatively, the ethylene polymer composition can becharacterized by an ATREF curve containing at least two peaks in thetemperature range from about 60 to about 110° C., and the differencebetween the temperatures of the two peaks (ΔT) can be in a range fromabout 17 to about 32° C., from about 18 to about 32° C., or from about18 to about 30° C. In these and other aspects, the peak ATREFtemperature (temperature of the highest peak on the ATREF curve) can beeither the lower temperature peak or the higher temperature peak. Infurther aspects, in addition to the aforementioned lower and highertemperature peaks, there are no other significant peaks on the ATREFcurve above a dW/dT of 1 in height (plot of dW/dT vs. T; normalized toan area equal to 1).

Consistent with aspects of this invention, the first ethylene polymercomponent and the second ethylene polymer component, independently, canbe produced using a zirconium-based metallocene catalyst system. Forexample, the catalyst system can comprise a zirconium-containingmetallocene compound (bridged or unbridged), an activator, and anoptional co-catalyst. In such aspects, the first ethylene polymercomponent and the second ethylene polymer component are not producedusing a hafnium-based and/or a titanium-based catalyst system.

Further, and independently, the ethylene polymer composition, the firstethylene polymer component, and the second ethylene polymer component,can contain no measurable amount of hafnium or titanium (catalystresidue), i.e., less than 0.1 ppm by weight. In some aspects, theethylene polymer composition, the first ethylene polymer component, andthe second ethylene polymer component, independently, can contain lessthan 0.08 ppm, less than 0.05 ppm, or less than 0.03 ppm, of eitherhafnium or titanium.

In an aspect, the ethylene polymer composition described herein can be areactor product (e.g., a single reactor product) containing the firstethylene polymer component and the second ethylene polymer component,for example, not a post-reactor blend of the first ethylene polymercomponent and the second ethylene polymer component. However, in anotheraspect of this invention, the ethylene polymer composition describedherein can be blend or mixture (e.g., a post-reactor blend) containingthe first ethylene polymer component and the second ethylene polymercomponent. The ethylene polymer composition can be in any suitable form,such as powder, fluff, or pellets.

Typically, a large majority or substantially all of the ethylene polymercomposition is the first ethylene polymer component and the secondethylene polymer component. In an aspect, the total amount of the firstethylene polymer component and the second ethylene polymer component inthe ethylene polymer composition can be at least about 75 wt. %, atleast about 85 wt. %, at least about 90 wt. %, at least about 95 wt. %,at least about 98 wt. %, or at least about 99 wt. %, and this is basedon the total weight of the composition. As one of skill in the art wouldreadily recognize, the ethylene polymer composition can further one ormore suitable additives, such as an antioxidant, an acid scavenger, anantiblock additive, a slip additive, a colorant, a filler, a polymerprocessing aid, a UV additive, and the like, as well as combinationsthereof. Further, as one of skill in the would readily recognize, theethylene polymer composition can further contain other polymercomponents—in addition to the first ethylene polymer component and thesecond ethylene polymer component—and illustrative and non-limitingpolymer components can include low density polyethylene (LDPE), ethylenevinyl acetate (EVA), and the like. In particular aspects of thisinvention, the only polymer components of the ethylene polymercomposition are the first ethylene polymer component and the secondethylene polymer component.

An illustrative and non-limiting example of an ethylene polymercomposition of the present invention can contain (i) ahomogeneously-branched first ethylene polymer component, and (ii) ahomogeneously-branched second ethylene polymer component of higherdensity than the first ethylene polymer component. The amount of thesecond ethylene polymer component can be in a range from about 4 toabout 50 wt. %, based on the total weight of the first ethylene polymercomponent and the second ethylene polymer component. Moreover, thecomposition can be characterized by a density in a range from about0.912 to about 0.925 g/cm³, a ratio of Mw/Mn in a range from about 1.8to about 4.5, a melt index less than or equal to about 3.5 g/10 min, aCY-a parameter in a range from about 0.25 to about 0.65, and an ATREFcurve containing at least two peaks, with a first peak at a temperaturein a range from about 67 to about 82° C., and a second peak at atemperature in a range from about 92 to about 105° C. This illustrativeand non-limiting example of an ethylene polymer composition consistentwith the present invention also can have any of the polymer propertiesand features listed herein and in any combination, unless indicatedotherwise.

Articles and Products

Articles of manufacture can be produced from, and/or can comprise, theethylene polymer compositions of this invention and, accordingly, areencompassed herein. For example, articles that can comprise ethylenepolymer compositions of this invention can include, but are not limitedto, an agricultural film, an automobile part, a bottle, a container forchemicals, a drum, a fiber or fabric, a food packaging film orcontainer, a food service article, a fuel tank, a geomembrane, ahousehold container, a liner, a molded product, a medical device ormaterial, an outdoor storage product, outdoor play equipment, a pipe, asheet or tape, a toy, or a traffic barrier, and the like. Variousprocesses can be employed to form these articles. Non-limiting examplesof these processes include injection molding, blow molding, rotationalmolding, film extrusion, sheet extrusion, profile extrusion,thermoforming, and the like. Additionally, additives and modifiers oftenare added to these polymer compositions in order to provide beneficialpolymer processing or end-use product attributes. Such processes andmaterials are described in Modern Plastics Encyclopedia, Mid-November1995 Issue, Vol. 72, No. 12; and Film Extrusion Manual—Process,Materials, Properties, TAPPI Press, 1992; the disclosures of which areincorporated herein by reference in their entirety. In some aspects ofthis invention, the article of manufacture can comprise (or can beproduced from) any of ethylene polymer compositions described herein,and the article of manufacture can be or can comprise a film.

In some aspects, the article produced from and/or comprising an ethylenepolymer composition of this invention is a film product. For instance,the film can be a blown film or a cast film that is produced from and/orcomprises any of the ethylene polymer compositions disclosed herein.Such films also can contain one or more additives, non-limiting examplesof which can include an antioxidant, an acid scavenger, an antiblockadditive, a slip additive, a colorant, a filler, a processing aid, a UVinhibitor, and the like, as well as combinations thereof.

Also contemplated herein is a method for making a film (e.g., a blownfilm, a cast film, etc.) comprising any ethylene polymer compositiondisclosed herein. For instance, the method can comprise melt processingthe ethylene polymer composition through a die to form the film.Suitably, the die can be configured based on the film to be produced,for example, an annular blown film die to produce a blown film, a slotor cast film die to produce a cast film, and so forth. Moreover, anysuitable means of melt processing can be employed, although extrusiontypically can be utilized. As above, additives can be combined with thepolymer composition in the melt processing step (extrusion step), suchas antioxidants, acid scavengers, antiblock additives, slip additives,colorants, fillers, processing aids, UV inhibitors, and the like, aswell as combinations thereof.

Films disclosed herein, whether cast or blown, can be any thickness thatis suitable for the particular end-use application, and often, theaverage film thickness can be in a range from about 0.25 to about 25mils, or from about 0.4 to about 20 mils. For certain film applications,typical average thicknesses can be in a range from about 0.5 to about 8mils, from about 0.8 to about 5 mils, from about 0.7 to about 2 mils, orfrom about 0.7 to about 1.5 mils.

In an aspect and unexpectedly, the films disclosed herein (e.g., blownfilms) can have excellent impact strength, tear resistance, and opticalproperties, despite the presence of the second ethylene polymercomponent (the higher density component). For instance, a filmconsistent with aspects of this invention can have a dart impactstrength greater than or equal to about 300 g/mil. In some aspects, thefilm can have a dart impact greater than or equal to about 400 g/mil,greater than or equal to about 500 g/mil, greater than or equal to about700 g/mil, greater than or equal to about 900 g/mil, greater than orequal to about 1200 g/mil, or greater than or equal to about 1400 g/mil,and often can range up to about 1500-2000 g/mil or more. For many filmapplications, the upper limit on dart impact is not determined, so longas the dart impact exceeds a particular minimal value or threshold.

The film also can be characterized by its Spencer impact strength.Spencer impact strengths often can be in a range from about 0.4 to about2 J/mil, or from about 0.5 to about 1.5 J/mil, but are not limitedthereto.

In another aspect, blown or cast films described herein can becharacterized by the MD (or TD) Elmendorf tear strength. Suitable rangesfor the MD tear strength can include, but are not limited to, from about100 to about 500 g/mil, from about 150 to about 500 g/mil, from about100 to about 450 g/mil, from about 125 to about 425 g/mil, from about150 to about 450 g/mil, from about 200 to about 450 g/mil, or from about225 to about 475 g/mil. Suitable ranges for the TD tear strength caninclude, but are not limited to, from about 200 to about 800 g/mil, fromabout 250 to about 800 g/mil, from about 250 to about 700 g/mil, or fromabout 300 to about 600 g/mil.

Advantageously, and unexpectedly, the film products of this inventionhave a good balance of tear properties, as generally quantified by theratio of MD Elmendorf tear strength to TD Elmendorf tear strength(MD:TD). Often, this MD:TD ratio falls in a range from about 0.3:1 toabout 0.8:1, from about 0.4:1 to about 0.8:1, from about 0.3:1 to about0.75:1, from about 0.4:1 to about 0.75:1, or from about 0.5:1 to about0.75:1.

In an aspect, film products of this invention (e.g., nominal 1-milfilms) also can be characterized by very good optical properties, suchas low haze and high clarity, e.g., particularly in the absence of anyadditives that might impact such measurements, such as slip andantiblock additives. Representative blown and cast films describedherein can have a film haze of less than or equal to about 12%, lessthan or equal to about 10%, in a range from about 2 to about 9%, or in arange from about 3 to about 8%, and often the film haze can range downto 1-3%. Similarly, the clarity of the films contemplated herein oftencan be at least about 95%, at least about 98%, at least about 98.5%, orat least about 99%.

An illustrative and non-limiting example of a film product (producedfrom or comprising the ethylene polymer composition) consistent with thepresent invention can have a MD Elmendorf tear strength in a range fromabout 100 to about 500 g/mil (or from about 150 to about 450 g/mil), anda ratio of MD Elmendorf tear strength to TD Elmendorf tear strength(MD:TD) in a range from about 0.3:1 to about 0.8:1 (or from about 0.4:1to about 0.75:1). This illustrative and non-limiting example of a filmproduct consistent with the present invention also can have any of thepolymer and film properties and features listed herein and in anycombination, unless indicated otherwise.

EXAMPLES

The invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, maysuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims.

Melt index (MI, g/10 min) was determined in accordance with ASTM D1238at 190° C. with a 2,160 gram weight, and high load melt index (HLMI,g/10 min) was determined in accordance with ASTM D1238 at 190° C. with a21,600 gram weight. Density was determined in grams per cubic centimeter(g/cm³) on a compression molded sample, cooled at 15° C. per hour, andconditioned for 40 hours at room temperature in accordance with ASTMD1505 and ASTM D4703.

Molecular weights and molecular weight distributions were obtained usinga PL-GPC 220 (Polymer Labs, an Agilent Company) system equipped with aIR4 detector (Polymer Char, Spain) and three Styragel HMW-6E GPC columns(Waters, MA) running at 145° C. The flow rate of the mobile phase1,2,4-trichlorobenzene (TCB) containing 0.5 g/L2,6-di-t-butyl-4-methylphenol (BHT) was set at 1 mL/min, and polymersolution concentrations were in the range of 1.0-1.5 mg/mL, depending onthe molecular weight. Sample preparation was conducted at 150° C. fornominally 4 hr with occasional and gentle agitation, before thesolutions were transferred to sample vials for injection. An injectionvolume of about 200 μL was used. The integral calibration method wasused to deduce molecular weights and molecular weight distributionsusing a Chevron Phillips Chemical Company's HDPE polyethylene resin,MARLEX® BHB5003, as the standard. The integral table of the standard waspre-determined in a separate experiment with SEC-MALS. Mn is thenumber-average molecular weight, Mw is the weight-average molecularweight, Mz is the z-average molecular weight, and Mp is the peakmolecular weight (location, in molecular weight, of the highest point ofthe molecular weight distribution curve).

Melt rheological characterizations were performed as follows.Small-strain (less than 10%) oscillatory shear measurements wereperformed on an Anton Paar MCR rheometer using parallel-plate geometry.All rheological tests were performed at 190° C. The complex viscosity|η*| versus frequency (ω) data were then curve fitted using the modifiedthree parameter Carreau-Yasuda (CY) empirical model to obtain thezero-shear viscosity—η₀, characteristic viscous relaxation time—τ_(η),and the breadth parameter—a (CY-a parameter). The simplifiedCarreau-Yasuda (CY) empirical model is as follows.

${{{\eta^{*}(\omega)}} = \frac{\eta_{0}}{\left\lbrack {1 + \left( {\tau_{\eta}\omega} \right)^{a}} \right\rbrack^{{({1 - n})}/a}}},$wherein: |η*(ω)|=magnitude of complex shear viscosity;

-   -   η₀=zero-shear viscosity;    -   τ_(η)=viscous relaxation time (Tau(η));    -   a=“breadth” parameter (CY-a parameter);    -   n=fixes the final power law slope, fixed at 2/11; and    -   ω=angular frequency of oscillatory shearing deformation.

Details of the significance and interpretation of the CY model andderived parameters can be found in: C. A. Hieber and H. H. Chiang,Rheol. Acta, 28, 321 (1989); C. A. Hieber and H. H. Chiang, Polym. Eng.Sci., 32, 931 (1992); and R. B. Bird, R. C. Armstrong and O. Hasseger,Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, 2nd Edition,John Wiley & Sons (1987); each of which is incorporated herein byreference in its entirety.

Differential Scanning Calorimetry (DSC) was performed at a heating rateof 20° C./min, as described in ASTM D3418 (2nd heat, peak temperaturesin ° C.).

The ATREF procedure was as follows. Forty mg of the polymer sample and20 mL of 1,2,4-trichlorobenzene (TCB) were sequentially charged into avessel on a PolyChar TREF 200+ instrument. After dissolving the polymer,an aliquot (500 microliters) of the polymer solution was loaded on thecolumn (stainless steel shots) at 150° C. and cooled at 0.5° C./min to25° C. Then, the elution was begun with a 0.5 mL/min TCB flow rate andheating at 1° C./min up to 120° C., and analyzing with an IR detector.The peak ATREF temperature is the location, in temperature, of thehighest point of the ATREF curve.

The long chain branches (LCB) per 1,000,000 total carbon atoms werecalculated using the method of Janzen and Colby (J. Mol. Struct.,485/486, 569-584 (1999)), from values of zero shear viscosity, η_(o)(determined from the Carreau-Yasuda model, described hereinabove), andmeasured values of Mw obtained using a Dawn EOS multiangle lightscattering detector (Wyatt). See also U.S. Pat. No. 8,114,946; J. Phys.Chem. 1980, 84, 649; and Y. Yu, D. C. Rohlfing, G. R Hawley, and P. J.DesLauriers, Polymer Preprints, 44, 49-50 (2003). These references areincorporated herein by reference in their entirety.

Short chain branch content and short chain branching distribution (SCBD)across the molecular weight distribution can be determined via anIR5-detected GPC system (IR5-GPC), wherein the GPC system is a PL220GPC/SEC system (Polymer Labs, an Agilent company) equipped with threeStyragel HMW-6E columns (Waters, MA) for polymer separation. Athermoelectric-cooled IR5 MCT detector (IR5) (Polymer Char, Spain) isconnected to the GPC columns via a hot-transfer line. Chromatographicdata is obtained from two output ports of the IR5 detector. First, theanalog signal goes from the analog output port to a digitizer beforeconnecting to Computer “A” for molecular weight determinations via theCirrus software (Polymer Labs, now an Agilent Company) and the integralcalibration method using a HDPE Marlex™ BHB5003 resin (Chevron PhillipsChemical) as the molecular weight standard. The digital signals, on theother hand, go via a USB cable directly to Computer “B” where they arecollected by a LabView data collection software provided by PolymerChar. Chromatographic conditions can be set as follows: column oventemperature of 145° C.; flowrate of 1 mL/min; injection volume of 0.4mL; and polymer concentration of about 2 mg/mL, depending on samplemolecular weight. The temperatures for both the hot-transfer line andIR5 detector sample cell are set at 150° C., while the temperature ofthe electronics of the IR5 detector is set at 60° C. Short chainbranching content can be determined via an in-house method using theintensity ratio of CH₃ (I_(CH3)) to CH₂ (I_(CH2)) coupled with acalibration curve. The calibration curve is a plot of SCB content(x_(SCB)) as a function of the intensity ratio of I_(CH3)/I_(CH2). Toobtain a calibration curve, a group of polyethylene resins (no less than5) of SCB level ranging from zero to ca. 32 SCB/1,000 total carbons (SCBStandards) are used. All these SCB Standards have known SCB levels andflat SCBD profiles pre-determined separately by NMR and thesolvent-gradient fractionation coupled with NMR (SGF-NMR) methods. UsingSCB calibration curves thus established, profiles of short chainbranching distribution across the molecular weight distribution areobtained for resins fractionated by the IR5-GPC system under exactly thesame chromatographic conditions as for these SCB standards. Arelationship between the intensity ratio and the elution volume isconverted into SCB distribution as a function of MWD using apredetermined SCB calibration curve (i.e., intensity ratio ofI_(CH3)/I_(CH2) vs. SCB content) and MW calibration curve (i.e.,molecular weight vs. elution time) to convert the intensity ratio ofI_(CH3)/I_(CH2) and the elution time into SCB content and the molecularweight, respectively.

Although not tested, it is expected that the polymer blend compositionsdiscussed below do not have a decreasing comonomer distribution, i.e.,the polymer blend compositions have either a reverse short chainbranching distribution (increasing comonomer distribution) or a flatshort chain branching distribution (uniform comonomer distribution).

Dart impact strength (g/mil) was measured in accordance with ASTM D1709(method A). Machine direction (MD) and transverse direction (TD)Elmendorf tear strengths (g/mil) were measured on a Testing Machinestear tester (Model 83-11-00) in accordance with ASTM D1922. SpencerImpact (J/mil) was determined in accordance with ASTM D3420.

Film haze (%) was determined in accordance with ASTM D1003, and filmclarity (%) was determined in accordance with ASTM 105.

Metals content, such as the amount of catalyst residue in the polymercomposition or film, was determined by ICP analysis on a PerkinElmerOptima 8300 instrument. Polymer samples were ashed in a Thermolynefurnace with sulfuric acid overnight, followed by acid digestion in aHotBlock with HCl and HNO₃ (3:1 v:v).

EXAMPLES 1-24

Low density polymer components (ethylene/1-hexene copolymers) were meltblended with high density polymer components (ethylene/1-hexenecopolymers or ethylene homopolymers) to produce Blend Examples B1-B15.The properties of the respective low density polymer components (LD 1 toLD 5) and high density polymer components (HD 1 to HD 3) are summarizedin Table I. These polymer components were produced using zirconium-basedmetallocene catalyst systems. The relative amounts of the low and highdensity components used in Blend Examples B1-B15, and the properties ofthe blend compositions, are summarized in Table II. The blendcompositions were produced using a Prism twin screw extruder with a 16″screw length. The heating and screw speed were adjusted to obtain a melttemperature of 275° C. for the polymer strand (Zone 1=193° C., Zone2=204° C., Zone 3=204° C., Zone 4=204° C., Zone 5=204° C., ScrewRPM=150). The polymer strand was cooled in a water bath, pelletized, andthen dried to form the polymer compositions of Blend Examples B1-B15.

Cast film samples at a 2-mil thickness (50 microns) were produced fromBlend Examples B1-B15 and low density components LD 1 to LD 5. The castfilm samples were made on a laboratory-scale cast film line usingtypical linear low density polyethylene conditions (LLDPE) as follows:127 mm die width, 0.508 mm die gap, 16 mm diameter single-screw extruder(L/D=24-27), 0.5 kg/hr output rate, and 204° C. barrel and die settemperatures. Cooling was accomplished with chill roll at about 23° C.These particular processing conditions were chosen because the cast filmproperties so obtained are typically representative of those obtainedfrom larger, commercial scale film casting conditions.

Table III summarizes the MD and TD Elmendorf tear strengths of the castfilm samples, and the ratios of MD:TD tear strength. Unexpectedly, theaddition of the higher density component to the low density componentresulted in an increase in the MD tear strength in all instances(compare B1-B3 versus LD 1, B4-B6 versus LD 2, and so forth). Further,the MD:TD tear strength ratio generally increased for Blend ExamplesB1-B15 (0.3-0.6 range), as compared to the corresponding LD 1 to LD 5low density components.

Low density polymer components (ethylene/1-hexene copolymers) were meltblended with a single high density polymer component (HD 1) to produceBlend Examples B16-B19. The blend compositions were produced using aZSK-40 twin screw extruder with a 30″ screw length. The heating andscrew speed were adjusted to obtain a melt temperature of 275° C. forthe polymer strand (Zone 1=250° C., Zone 2=245° C., Zone 3=245° C., Zone4=230° C., Screw RPM=75). The relative amounts of the low and highdensity components used in Blend Examples B16-B19, and the properties ofthe blend compositions, are summarized in Table IV.

FIG. 1 illustrates the second heat DSC curves for low density componentLD 1, high density component HD 1, and ethylene polymer composition B16.The low density component LD 1 and the ethylene polymer composition B16both have two peaks on their respective DSC curves (and arerepresentative of the other low density components and ethylene polymercompositions of this invention), while the high density component HD 1has only a single peak (and is representative of the other high densitycomponents of this invention).

Blown film samples at a 1-mil thickness (25 microns) were produced fromBlend Examples B16-B19 and low density components LD 1 to LD 5. Theblown film samples were made on a laboratory-scale blown film line usingtypical linear low density polyethylene conditions (LLDPE) as follows:100 mm die diameter, 1.5 mm die gap, 37.5 mm diameter single-screwextruder fitted with a barrier screw with a Maddock mixing section atthe end (L/D=24, 2.2:1 compression ratio), 27 kg/hr output rate, 2.5:1blow-up ratio (BUR), “in-pocket” bubble with a “frost line height” (FLH)of about 28 cm, and 190° C. barrel and die set temperatures. Cooling wasaccomplished with a Dual Lip air ring using ambient (laboratory) air atabout 25° C. These particular processing conditions were chosen becausethe blown film properties so obtained are typically representative ofthose obtained from larger, commercial scale film blowing conditions.

Table V summarizes the dart impact, Spencer impact, MD and TD Elmendorftear strength, ratio of MD:TD tear strength, and optical properties ofthe blown film samples. Similar to Table III, and unexpectedly, theaddition of the high density component to the low density componentresulted in an increase in the MD tear strength in all instances(compare B16 versus LD 1, B17 versus LD 2, and so forth). Further, theMD:TD tear strength ratio generally increased for Blend Examples B16-B19(0.36-0.72 range), as compared to the corresponding LD 1 to LD 4 lowdensity components. Also beneficially, the addition of the high densitycomponent to the low density component did not significantly decreasethe dart impact, spencer impact, film haze, or film clarity. BlendExamples B16-B19 retained excellent impact strength and opticalproperties, but with an increase in MD tear resistance (and arerepresentative of the ethylene polymer compositions of this invention).

The representative blown film samples of Blend Examples B16-B19 wereanalyzed for residual metals, and the zirconium content was in the0.2-0.8 ppm range (by weight). The titanium content and hafnium contentwere less than 0.03 ppm, which was below the level of detection (nomeasurable amount).

A single low density polymer component (ethylene/1-hexene copolymer) wasmelt blended with high density homopolymer components to produce BlendExamples B20-B24, in the same manner as Blend Examples B1-B15. Theproperties of the respective low density polymer component (LD 6) andhigh density polymer components (HD 4 to HD 8) are summarized in TableVI. These polymer components were produced using zirconium-basedmetallocene catalyst systems. The relative amounts of the low and highdensity components used in Blend Examples B20-B24, and the properties ofthe blend compositions, are summarized in Table VII and Table VIII. Asshown in the tables, the high density polymer components (HD 4 to HD 8)covered a large range of melt index (from 0.1 to 39 g/10 min) andmolecular weight (Mw from 49 to 223 kg/mol). However, the blendcompositions of Examples B20-B24 had a much narrower range of polymerattributes (density, MI, HLMI, HLMI/MI, Mw, Mw/Mn, Mz/Mw, η₀, and CY-a).

Cast film samples at a 2-mil thickness (50 microns) were produced fromBlend Examples B20-B24 and low density component LD 6, in the samemanner as Blend Examples B1-B15. Table IX summarizes the MD and TDElmendorf tear strengths of the cast film samples, and the ratio ofMD:TD tear strength. With the exception of Example B20 (which used thehighest molecular weight high density component), the addition of thehigh density component to the low density component resulted in asignificant increase in the MD tear strength (increases of 50-75%).Blend Example B22 had the best tear resistance, and utilized the highdensity component that was most similar in molecular weight to that ofthe low density component. However, higher melt flow (lower Mw) highdensity components also resulted in significant increases in tearstrength. Further, despite the films being produced using a cast filmprocess, the MD:TD tear strength ratios for Blend Examples B21-B24ranged from 0.43 to 0.47.

FIG. 2 illustrates the ATREF profiles of the ethylene polymercompositions of Blend Examples B1-B6, while FIG. 3 illustrates the ATREFprofiles of the ethylene polymer compositions of Blend Examples B16-B19,and these ATREF profiles are representative of the ethylene polymercompositions of this invention. These ATREF curves generally contain twopeaks in the 60-110° C. range, with the first peak (lower temperaturepeak) at a temperature in the 70-80° C. range, and with the second peak(higher temperature peak) at a temperature in the 94-105° C. range. Thepeak temperatures for Examples B16-B19 are summarized in Table X.

FIG. 4 presents an “Arnett plot,” wherein the log of the zero-shearviscosity is plotted against the log of the weight-average molecularweight, for Blend Examples B1-B15, and is representative of the ethylenepolymer compositions of this invention. When each point is compared tothe Janzen-Colby grid lines, the average number of long chain branches(LCB) in the polymer can be determined (Alpha is the average number ofLCB per carbon atom). FIG. 4 shows the unexpectedly low levels of LCB ofthe polymer compositions of this invention, with less than 10 LCB per1,000,000 total carbon atoms, and in some cases, less than 1-3 LCB per1,000,000 total carbon atoms.

Thus, the polymer compositions disclosed herein offer a beneficialcombination of density, molecular weight, melt flow, and ATREFproperties, resulting in film products with excellent impact resistanceand optical properties, but with improved tear resistance, particularlyin the machine direction, as quantified by the MD Elmendorf tearstrength.

TABLE I Polymer Density MI Mw η₀ Component (g/cm³) (g/10 min) (kg/mol)Mw/Mn (Pa-sec) CY-a Low Density Components LD 1 0.911 1.03 125 2.237,150 0.605 LD 2 0.912 1.01 122 3.28 12,000 0.311 LD 3 0.913 0.90 1282.62 8,250 0.601 LD 4 0.917 1.52 111 3.82 6,950 0.379 LD 5 0.913 1.40114 2.10 4,350 0.604 High Density Components HD 1 0.958 1.04 135 2.986,700 0.564 HD 2 0.947 0.86 145 2.63 9,380 0.512 HD 3 0.932 0.90 1372.57 5,670 0.465

TABLE II Blend Low Density LD content High Density HD content Density MwExample Component (wt. %) Component (wt. %) (g/cm³) (kg/mol) Mw/Mn B1 LD1 79.4 HD 1 20.6 0.920 125 2.59 B2 LD 1 74.0 HD 2 26.0 0.920 133 2.55 B3LD 1 60.1 HD 3 39.9 0.920 131 2.59 B4 LD 2 87.6 HD 1 12.4 0.917 127 3.36B5 LD 2 84.0 HD 2 16.0 0.919 130 3.39 B6 LD 2 73.5 HD 3 26.5 0.918 1303.35 B7 LD 3 90.4 HD 1 9.6 0.916 135 270 B8 LD 3 87.4 HD 2 12.6 0.917137 2.76 B9 LD 3 78.6 HD 3 21.4 0.917 137 2.64  B10 LD 4 93.8 HD 1 6.20.920 121 3.99  B11 LD 4 91.8 HD 2 8.2 0.921 122 3.89  B12 LD 4 85.5 HD3 14.5 0.920 123 3.73  B13 LD 5 95.0 HD 1 5.0 0.915 124 2.50  B14 LD 593.3 HD 2 6.7 0.915 124 2.53  B15 LD 5 88.0 HD 3 12.0 0.918 127 2.50

TABLE III Component MD Tear TD Tear Ratio of or Blend (g/mil) (g/mil)MD/TD B1 308 579 0.53 B2 287 532 0.54 B3 271 562 0.48 LD 1 172 418 0.41B4 179 487 0.37 B5 155 486 0.32 B6 144 485 0.30 LD 2 109 355 0.31 B7 227437 0.52 B8 214 510 0.42 B9 212 421 0.50 LD 3 112 445 0.25 B10 213 4900.43 B11 224 492 0.46 B12 230 510 0.45 LD 4 140 519 0.27 B13 255 4350.59 B14 215 382 0.56 B15 227 449 0.51 LD 5 188 371 0.51

TABLE IV Blend Low Density LD content High Density HD content Density MIMw Example Component (wt. %) Component (wt. %) (g/cm³) (g/10 min)(kg/mol) Mw/Mn B16 LD 1 79 HD 1 21 0.920 1.05 121 2.41 B17 LD 2 88 HD 112 0.917 1.03 118 3.18 B18 LD 3 90 HD 1 10 0.916 0.89 125 2.35 B19 LD 496 HD 1 4 0.919 1.45 110 3.94

TABLE V Dart Spencer MD TD Component Impact Impact Tear Tear Ratio ofHaze Clarity or Blend (g/mil) (J/mil) (g/mil) (g/mil) MD/TD (%) (%) LD5 >1400 1.72 228 350 0.65 4.7 98.9 LD 1 >1400 1.68 202 335 0.60 3.2 99.2B16 >1400 1.16 349 484 0.72 7.2 98.6 LD 2 >1400 No Break 158 349 0.454.4 — B17 898 0.69 177 488 0.36 6.8 98.8 LD 3 >1400 1.67 223 350 0.643.0 99.3 B18 >1400 1.34 293 435 0.67 5.4 99.0 LD 4 904 0.88 197 449 0.445.4 98.8 B19 712 0.56 272 499 0.55 6.8 98.8

TABLE VI MI Density Mn Mw η₀ Component (g/10 min) (g/cm³) (kg/mol)(kg/mol) Mw/Mn Mz/Mw (Pa-sec) CY-a HD 4 0.12 0.950 90 223 2.48 1.7958,000 0.553 HD 5 0.50 0.955 60 154 2.57 1.83 13,400 0.572 HD 6 1.040.957 49 128 2.62 1.89 6,830 0.579 HD 7 38.6 0.971 13 49 3.71 2.34 1920.466 HD 8 10.3 0.966 19 68 3.59 2.15 680 0.567 LD 6 1.19 0.911 50 1172.31 1.75 4,210 0.560

TABLE VII Mw of HD LD HD Blend Low Density High Density Componentcontent content Example Component Component (kg/mol) (wt. %) (wt. %) B20LD 6 HD 4 223 81.7 18.3 B21 LD 6 HD 5 154 83.6 16.4 B22 LD 6 HD 6 12884.5 15.5 B23 LD 6 HD 8 68 86.8 13.2 B24 LD 6 HD 7 49 87.8 12.2

TABLE VIII Blend Density MI HLMI Mw η₀ Example (g/cm³) (g/10 min) (g/10min) HLMI/MI (kg/mol) Mw/Mn Mz/Mw (Pa-sec) CY-a B20 0.918 0.74 12.9 17.4137 2.48 1.91 10,800 0.535 B21 0.917 1.09 18.2 16.7 120 2.35 1.73 7,0000.602 B22 0.917 1.20 20.2 16.9 116 2.46 1.74 6,200 0.608 B23 0.917 1.6128.7 17.8 104 2.68 1.74 4,700 0.618 B24 0.918 1.59 28.1 17.7 102 2.821.79 4,700 0.617

TABLE IX Mw of HD MD TD Component High Density Component Tear Tear Ratioof or Blend Component (kg/mol) (g/mil) (g/mil) MD/TD B20 HD 4 223 155674 0.23 B21 HD 5 154 275 642 0.43 B22 HD 6 128 300 633 0.47 B23 HD 8 68272 605 0.45 B24 HD 7 49 264 570 0.46 LD 6 N/A N/A 170 302 0.56

TABLE X Low High Temperature Temperature Blend Example Peak (° C.) Peak(° C.) B16 71 99 B17 76 100 B18 75 98 B19 80 99

The invention is described above with reference to numerous aspects andspecific examples. Many variations will suggest themselves to thoseskilled in the art in light of the above detailed description. All suchobvious variations are within the full intended scope of the appendedclaims. Other aspects of the invention can include, but are not limitedto, the following (aspects are described as “comprising” but,alternatively, can “consist essentially of” or “consist of”):

Aspect 1. An ethylene polymer composition comprising:

(i) a homogeneously-branched first ethylene polymer component; and

(ii) a homogeneously-branched second ethylene polymer component ofhigher density than the first ethylene polymer component;

wherein the amount of the second ethylene polymer component is in arange from about 4 to about 50 wt. %, based on the total weight of thefirst ethylene polymer component and the second ethylene polymercomponent; and

wherein the composition is characterized by:

-   -   a density in a range from about 0.912 to about 0.925 g/cm³;    -   a melt index less than or equal to about 3.5 g/10 min; and    -   a CY-a parameter in a range from about 0.25 to about 0.65.

Aspect 2. The composition defined in aspect 1, wherein the compositionhas a density in any range disclosed herein, e.g., from about 0.912 toabout 0.922 g/cm³, from about 0.912 to about 0.92 g/cm³, from about0.915 to about 0.925 g/cm³, etc.

Aspect 3. The composition defined in aspect 1 or 2, wherein the firstethylene polymer component has a density in any range disclosed herein,e.g., from about 0.89 to about 0.922 g/cm³, from about 0.90 to about0.92 g/cm³, from about 0.905 to about 0.918 g/cm³, from about 0.91 toabout 0.918 g/cm³, etc.

Aspect 4. The composition defined in any one of aspects 1-3, wherein thesecond ethylene polymer component has a density in any range disclosedherein, e.g., from about 0.93 to about 0.972 g/cm³, from about 0.932 toabout 0.97 g/cm³, from about 0.93 to about 0.958 g/cm³, from about 0.945to about 0.968 g/cm³, etc.

Aspect 5. The composition defined in any one of aspects 1-4, wherein theamount of the second ethylene polymer component is in any rangedisclosed herein, e.g., from about 4 to about 40 wt. %, from about 4 toabout 25 wt. %, from about 4 to about 15 wt. %, from about 10 to about40 wt. %, from about 10 to about 25 wt. %, from about 20 to about 30 wt.%, etc., based on the total weight of the first ethylene polymercomponent and the second ethylene polymer component

Aspect 6. The composition defined in any one of aspects 1-5, wherein thecomposition and the first ethylene polymer component, independently,have a melt index (MI) in any range disclosed herein, e.g., less than orequal to about 3.5 g/10 min, less than or equal to about 2.5 g/10 min,less than or equal to about 1.5 g/10 min, from about 0.3 to about 2 g/10min, from about 0.5 to about 1.8 g/10 min, from about 0.7 to about 1.7g/10 min, etc.

Aspect 7. The composition defined in any one of aspects 1-6, wherein thesecond ethylene polymer component has a melt index (MI) in any rangedisclosed herein, e.g., less than or equal to about 50 g/10 min, lessthan or equal to about 40 g/10 min, less than or equal to about 10 g/10min, from about 0.3 to about 2 g/10 min, from about 0.5 to about 40 g/10min, from about 0.4 to about 12 g/10 min, etc.

Aspect 8. The composition defined in any one of aspects 1-7, wherein thecomposition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a CY-a parameter in anyrange disclosed herein, e.g., from about 0.25 to about 0.65, from about0.25 to about 0.6, from about 0.3 to about 0.65, from about 0.35 toabout 0.65, from about 0.4 to about 0.65, from about 0.45 to about 0.65,etc.

Aspect 9. The composition defined in any one of aspects 1-8, wherein thecomposition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a reverse short chainbranching distribution (increasing comonomer distribution), e.g., thenumber of SCB per 1000 total carbon atoms of the polymer at Mw isgreater than at Mn, and/or the number of SCB per 1000 total carbon atomsof the polymer at Mz is greater than at Mw, and/or the number of SCB per1000 total carbon atoms of the polymer at Mz is greater than at Mn.

Aspect 10. The composition defined in any one of aspects 1-8, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a flat short chainbranching distribution (uniform comonomer distribution), e.g., a slopeof a plot of the number of short chain branches per 1000 total carbonatoms versus the logarithm of molecular weight of the olefin polymer(determined via linear regression over the range from D15 to D85) is ina range from about −0.6 to about 0.6, and/or a percentage of data pointsdeviating from the average short chain branch content by greater than0.5 short chain branches per 1000 total carbon atoms (determined overthe range from D15 to D85) is less than or equal to about 20%, and/or apercentage of data points deviating from the average short chain branchcontent by greater than 1 short chain branch per 1000 total carbon atoms(determined over the range from D15 to D85) is less than or equal toabout 10%.

Aspect 11. The composition defined in any one of aspects 1-10, whereinthe first ethylene polymer component and the second ethylene polymercomponent, independently, are produced using a zirconium-basedmetallocene catalyst system.

Aspect 12. The composition defined in any one of aspects 1-11, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of HLMI/MI inany range disclosed herein, e.g., from about 10 to about 35, from about15 to about 35, from about 15 to about 28, from about 15 to about 25,from about 12 to about 30, from about 12 to about 22, etc.

Aspect 13. The composition defined in any one of aspects 1-12, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of Mw/Mn in anyrange disclosed herein, e.g., from about 1.8 to about 4.5, from about 2to about 4, from about 2.2 to about 4, from about 2.2 to about 3.8, etc.

Aspect 14. The composition defined in any one of aspects 1-13, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of Mz/Mw in anyrange disclosed herein, e.g., from about 1.6 to about 2.5, from about1.7 to about 2.3, from about 1.8 to about 2.3, from about 1.7 to about2.1, etc.

Aspect 15. The composition defined in any one of aspects 1-14, whereinthe composition and the first ethylene polymer component, independently,have a Mw in any range disclosed herein, e.g., from about 85 to about200 kg/mol, from about 85 to about 150 kg/mol, from about 100 to about200 kg/mol, from about 100 to about 180 kg/mol, from about 100 to about150 kg/mol, etc.

Aspect 16. The composition defined in any one of aspects 1-15, whereinthe second ethylene polymer component has a Mw in any range disclosedherein, e.g., from about 85 to about 200 kg/mol, from about 85 to about160 kg/mol, from about 100 to about 200 kg/mol, from about 40 to about180 kg/mol, from about 40 to about 150 kg/mol, etc.

Aspect 17. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 1.1:1 to about 2.5:1, from about 1.1:1 to about 2:1,from about 1.1:1 to about 1.8:1, from about 1.2:1 to about 2.5:1, etc.

Aspect 18. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 0.5:1 to about 0.9:1, from about 0.6:1 to about 0.9:1,from about 0.65:1 to about 0.9:1, from about 0.7:1 to about 0.9:1, etc.

Aspect 19. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 0.75:1 to about 1.25:1, from about 0.8:1 to about1.2:1, from about 0.9:1 to about 1.1:1, from about 0.8:1 to about 1.1:1,etc.

Aspect 20. The composition defined in any one of aspects 1-19, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a unimodal molecularweight distribution.

Aspect 21. The composition defined in any one of aspects 1-20, whereinthe composition and the first ethylene polymer component, independently,have a zero-shear viscosity in any range disclosed herein, e.g., fromabout 2,500 to about 25,000 Pa-sec, from about 3,000 to about 25,000Pa-sec, from about 2,500 to about 20,000 Pa-sec, from about 3,000 toabout 20,000 Pa-sec, etc.

Aspect 22. The composition defined in any one of aspects 1-21, whereinthe second ethylene polymer component has a zero-shear viscosity in anyrange disclosed herein, e.g., from about 2,500 to about 25,000 Pa-sec,from about 5,000 to about 70,000 Pa-sec, from about 150 to about 2,500Pa-sec, from about 500 to about 5,000 Pa-sec, etc.

Aspect 23. The composition defined in any one of aspects 1-22, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, contain no measurable amountof hafnium or titanium.

Aspect 24. The composition defined in any one of aspects 1-23, whereinthe first ethylene polymer component and the second ethylene polymercomponent, independently, are not produced using a hafnium-based and/ortitanium-based catalyst system.

Aspect 25. The composition defined in any one of aspects 1-24, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, contain less than 10 longchain branches (LCB), less than 8 LCB, less than 5 LCB, less than 3 LCB,etc., per million total carbon atoms.

Aspect 26. The composition defined in any one of aspects 1-25, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks, with a first peak (lower temperature peak) at a temperaturein any range disclosed herein, e.g., from about 67 to about 82° C., fromabout 70 to about 82° C., from about 68 to about 80° C., etc.

Aspect 27. The composition defined in any one of aspects 1-26, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks, with a second peak (higher temperature peak) at a temperaturein any range disclosed herein, e.g., from about 92 to about 105° C.,from about 95 to about 105° C., from about 96 to about 105° C., etc.

Aspect 28. The composition defined in any one of aspects 1-27, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks in the temperature range from about 65 to about 105° C., andthe difference between the temperatures of the two peaks (ΔT) is in anyrange disclosed herein, e.g., from about 17 to about 32° C., from about18 to about 32° C., from about 18 to about 30° C., etc.

Aspect 29. The composition defined in any one of aspects 1-28, whereinthe composition is a single reactor product, e.g., not a post-reactorblend.

Aspect 30. The composition defined in any one of aspects 1-28, whereinthe composition is a post-reactor blend.

Aspect 31. The composition defined in any one of aspects 1-30, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylenehomopolymer and/or an ethylene/α-olefin copolymer.

Aspect 32. The composition defined in any one of aspects 1-31, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylenehomopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexenecopolymer, and/or an ethylene/1-octene copolymer.

Aspect 33. The composition defined in any one of aspects 1-32, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylene/1-butenecopolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octenecopolymer.

Aspect 34. The composition defined in any one of aspects 1-33, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylene/1-hexenecopolymer.

Aspect 35. The composition defined in any one of aspects 1-34, whereinthe total amount of the first ethylene polymer component and the secondethylene polymer component in the composition is in any range disclosedherein, e.g., at least about 75 wt. %, at least about 85 wt. %, at leastabout 90 wt. %, at least about 95 wt. %, etc., based on the total weightof the composition.

Aspect 36. The composition defined in any one of aspects 1-35, whereinthe composition further comprises any additive disclosed herein, e.g.,an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,etc., or combinations thereof.

Aspect 37. An article of manufacture comprising (or produced from) thecomposition defined in any one of aspects 1-36.

Aspect 38. An article of manufacture comprising (or produced from) thecomposition defined in any one of aspects 1-36, wherein the article isan agricultural film, an automobile part, a bottle, a container forchemicals, a drum, a fiber or fabric, a food packaging film orcontainer, a food service article, a fuel tank, a geomembrane, ahousehold container, a liner, a molded product, a medical device ormaterial, an outdoor storage product, outdoor play equipment, a pipe, asheet or tape, a toy, or a traffic barrier.

Aspect 39. A film comprising (or produced from) the polymer compositiondefined in any one of aspects 1-36.

Aspect 40. The film defined in aspect 39, wherein the film has a haze(with or without additives) in any range disclosed herein, e.g., lessthan or equal to about 12%, less than or equal to about 10%, from about2 to about 9%, from about 3 to about 8%, etc.

Aspect 41. The film defined in aspect 39 or 40, wherein the film has aclarity (with or without additives) in any range disclosed herein, e.g.,at least about 95%, at least about 98%, at least about 98.5%, at leastabout 99%, etc.

Aspect 42. The film defined in any one of aspects 39-41, wherein thefilm has a dart impact strength in any range disclosed herein, e.g.,greater than or equal to about 500 g/mil, greater than or equal to about700 g/mil, greater than or equal to about 900 g/mil, greater than orequal to about 1400 g/mil, etc.

Aspect 43. The film defined in any one of aspects 39-42, wherein thefilm has a Spencer impact strength in any range disclosed herein, e.g.,from about 0.4 to about 2 J/mil, from about 0.5 to about 1.5 J/mil, etc.

Aspect 44. The film defined in any one of aspects 39-43, wherein thefilm has a MD Elmendorf tear strength in any range disclosed herein,e.g., from about 100 to about 500 g/mil, from about 100 to about 450g/mil, from about 125 to about 425 g/mil, from about 150 to about 450g/mil, from about 200 to about 450 g/mil, etc.

Aspect 45. The film defined in any one of aspects 39-44, wherein thefilm has a TD Elmendorf tear strength in any range disclosed herein,e.g., from about 200 to about 800 g/mil, from about 250 to about 700g/mil, from about 300 to about 600 g/mil, etc.

Aspect 46. The film defined in any one of aspects 39-45, wherein thefilm has a ratio of MD Elmendorf tear strength to TD Elmendorf tearstrength (MD:TD) in any range disclosed herein, e.g., from about 0.3:1to about 0.8:1, from about 0.4:1 to about 0.8:1, from about 0.3:1 toabout 0.75:1, from about 0.4:1 to about 0.75:1, from about 0.5:1 toabout 0.75:1, etc.

Aspect 47. The film defined in any one of aspects 39-46, wherein thefilm has an average thickness in any range disclosed herein, e.g., fromabout 0.4 to about 20 mils, from about 0.5 to about 8 mils, from about0.8 to about 5 mils, from about 0.7 to about 2 mils, from about 0.7 toabout 1.5 mils, etc.

Aspect 48. The film defined in any one of aspects 39-47, wherein thefilm is a blown film.

Aspect 49. The film defined in any one of aspects 39-47, wherein thefilm is a cast film.

We claim:
 1. An ethylene polymer composition comprising: (i) ahomogeneously-branched first ethylene polymer component; and (ii) ahomogeneously-branched second ethylene polymer component of higherdensity than the first ethylene polymer component, the second ethylenepolymer component having a density in a range from about 0.945 to about0.968 g/cm³; wherein the amount of the second ethylene polymer componentis in a range from about 10 to about 25 wt. %, based on the total weightof the first ethylene polymer component and the second ethylene polymercomponent; and wherein the composition is characterized by: a density ina range from about 0.912 to about 0.925 g/cm³; a Mw in a range fromabout 85 to about 200 kg/mol; a ratio of Mw/Mn in a range from about 2to about 3; a melt index in a range from about 0.3 to about 2 g/10 min;a CY-a parameter in a range from about 0.4 to about 0.65; and an ATREFcurve containing at least two peaks, with a first peak at a temperaturein a range from about 67 to about 82° C., and a second peak at atemperature in a range from about 95 to about 105° C.
 2. An article ofmanufacture comprising the composition of claim
 1. 3. The composition ofclaim 1, wherein the difference between the temperatures (ΔT) of thefirst peak and the second peak is in a range from about 17 to about 32°C.
 4. The composition of claim 1, wherein the composition comprises anethylene homopolymer, an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or anycombination thereof.
 5. The composition of claim 4, wherein thecomposition is further characterized by: a ratio of Mz/Mw in a rangefrom about 1.7 to about 2.3; and a ratio of HLMI/MI in a range fromabout 15 to about
 35. 6. The composition of claim 4, wherein thecomposition is a single reactor product.
 7. The composition of claim 4,wherein the composition is a post-reactor blend.
 8. A blown filmcomprising the composition of claim
 4. 9. The blown film of claim 8,wherein the blown film has: a haze of less than or equal to about 10%; adart impact strength of greater than or equal to about 500 g/mil; and aMD Elmendorf tear strength in a range from about 100 to about 450 g/mil.10. The blown film of claim 9, wherein: the haze is in a range fromabout 3 to about 8%; the MD Elmendorf tear strength is in a range fromabout 125 to about 425 g/mil; the blown film has a ratio of MD Elmendorftear strength to TD Elmendorf tear strength (MD:TD) in a range fromabout 0.3:1 to about 0.8:1; and the blown film has an average thicknessin a range from about 0.5 to about 8 mils.
 11. The composition of claim1, wherein: the melt index is in a range from about 0.5 to about 1.8g/10 min; and the composition comprises an ethylene homopolymer, anethylene/l-butene copolymer, an ethylene/l-hexene copolymer, anethylene/l-octene copolymer, or any combination thereof.
 12. Thecomposition of claim 11, wherein the first ethylene polymer componenthas a ratio of HLMI/MI in a range from about 12 to about
 22. 13. Thecomposition of claim 11, wherein the first ethylene polymer componenthas a CY-a parameter in a range from about 0.45 to about 0.65.
 14. Thecomposition of claim 11, wherein the second ethylene polymer componenthas a ratio of HLMI/MI in a range from about 12 to about
 22. 15. Thecomposition of claim 11, wherein the second ethylene polymer componenthas a CY-a parameter in a range from about 0.45 to about 0.65.
 16. Thecomposition of claim 11, wherein the second ethylene polymer componenthas a melt index in a range from about 0.5 to about 40 g/10 min.
 17. Thecomposition of claim 11, wherein the composition is furthercharacterized by: a ratio of Mz/Mw in a range from about 1.7 to about2.3; and a ratio of HLMI/MI in a range from about 15 to about
 35. 18.The composition of claim 17, wherein the second ethylene polymercomponent has a melt index in a range from about 0.5 to about 40 g/10min.
 19. The composition of claim 18, wherein the first ethylene polymercomponent has a density in a range from about 0.905 to about 0.918g/cm³.
 20. An article of manufacture comprising the composition of claim19.
 21. The composition of claim 11, wherein the composition containsless than 0.05 ppm, independently, of hafnium and titanium.
 22. Thecomposition of claim 11, wherein the composition has a unimodalmolecular weight distribution.
 23. The composition of claim 11, whereinthe first ethylene polymer component has a density in a range from about0.905 to about 0.918 g/cm³.
 24. The composition of claim 23, wherein thedifference between the temperatures (AT) of the first peak and thesecond peak is in a range from about 18 to about 30° C.
 25. Thecomposition of claim 23, wherein the first peak is at a temperature in arange from about 68 to about 80° C.
 26. The composition of claim 11,wherein the first ethylene polymer component has a density in a rangefrom about 0.91 to about 0.918 g/cm³.
 27. The composition of claim 26,wherein the melt index is in a range from about 0.7 to about 1.7 g/10min.
 28. An article of manufacture comprising the composition of claim27.